1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?

2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).

3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?

1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?

2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).

3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?

Thanks!

Yes.

Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND.

Pushbutton and S-Trigger have the same function. And you can use on to connect with the Audio trigger output, to get some weird self-trigger function. (Emphasis on weird).

Gate is an ordinary 5V positive-going Voltage Trigger ("Gate") input.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?

2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).

3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?

Thanks!

Yes.

Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND.

Pushbutton and S-Trigger have the same function. And you can use on to connect with the Audio trigger output, to get some weird self-trigger function. (Emphasis on weird).

Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?

Thanks!

linear

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?

Thanks!

linear

JH.

Anything between 10k and 100k will do.
Recommended: 10k

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.

I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.

Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.

One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.

I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.

Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.

Thanks!

The VCA core is using the very same signal levels as the EMS VCS3.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Thanks, but I'm still not clear on what effect the input signal level has when using the buffered inputs versus the core inputs.

Maybe it makes more sense to ask this way - if I'm using this module in a modular synth with 10Vp-p signals, would it make sense to use the buffered input as shown in the schematic, with R56=10K? Would this configuration "massage" the signal to make it more appropriate for the circuit? Then I could adjust R70 on the buffered output to bring the level back up to 10Vp-p? If so, does this mean I would have a problem with using this module with a synth with outputs closer to instrument level, and for that would I then want core inputs as well? Just trying to figure out which inputs would be appropriate given my situation and if there would be any reason to have one of each. Again, I understand the other things about using buffered inputs and outputs, just trying to figure out the input signal level aspect as it regards this circuit.

Thanks again.

jhaible wrote:

numbertalk wrote:

Thank you very kindly for the timely response.

One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.

I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.

Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.

It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.

So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?

Thanks again!

jhaible wrote:

It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.

Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.

So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?

Thanks again!

jhaible wrote:

It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.

JH.

_________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Also, for anyone using the BOM that was attached earlier, it specifies a 1M trimmer but from the schematic looks like it should be 2M.

jhaible wrote:

10k log (audio taper) would be a good value for the attenuator(s).

JH.

numbertalk wrote:

Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.

So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?

Thanks again!

jhaible wrote:

It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.

Also, for anyone using the BOM that was attached earlier, it specifies a 1M trimmer but from the schematic looks like it should be 2M.

jhaible wrote:

10k log (audio taper) would be a good value for the attenuator(s).

JH.

numbertalk wrote:

Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.

So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?

Thanks again!

jhaible wrote:

It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.

JH.

_________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that?

One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that?

This depends on the knob response you prefer.
My preference is to use no attenator pot at the oinput for the Decay CV at all. but use a 10k linear pot at the DeacyCVPol connector instead: Then you have a (linear) reversible attenuator.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that?

This depends on the knob response you prefer.
My preference is to use no attenator pot at the oinput for the Decay CV at all. but use a 10k linear pot at the DeacyCVPol connector instead: Then you have a (linear) reversible attenuator.

In a system with input attenuators (most modular concepts) you should add an input attenuator potentiometer, or better a reversible attenuator, for the Decay Time CV.

In an EMS-like system, where there are no input attenuators, you should have an *output* attenuator for each output, typically a 5k log potentiometer.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

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